Test Python Format in wiki

Edit 0 1 … 
import turtle
wn = turtle.Screen()
alex = turtle.Turtle()
i=140
alex.penup()
alex.goto(0,-100)
alex.pendown()
alex.speed(20)
step=0
while i>10:
    step+=1
    i=i-10
    if step%2==1:
        alex.fillcolor('black')
    else:
        alex.fillcolor('yellow')
        alex.begin_fill()
        alex.circle(i)
        alex.end_fill()
        alex.penup()
        alex.left(90)
        alex.forward(10)
        alex.pendown()
        alex.right(90)
 
wn.mainloop()